An unusual presentation of Pseudomonas citronellolis bacteraemia and Campylobacter gastroenteritis infection in a human – a case report and literature review

Introduction. Pseudomonas citronellolis is an unusual pathogen in humans and has not been extensively described in the scientific literature. Herein, we present a case of bacteremia and septic shock due to Pseudomonas citronellolis following Campylobacter species gastroenteritis in a patient with immunosuppression. Case Presentation. An 80-year-old man with myeloproliferative disorder on ruxolitinib presented with several days of worsening abdominal pain, which rapidly developed into septic shock with multi-organ failure and explosive diarrhea. Gram-negative bacilli observed on Gram staining of his blood culture broth were later identified as Pseudomonas citronellolis and Bacteroides thetaiotaomicron . Repeated abdominal imaging revealed no evidence of intestinal perforation or megacolon. In addition, stool PCR was positive for Campylobacter species. His clinical course improved after 14 days of meropenem with complete resolution of his symptoms and organ failure. Conclusion. P. citronellolis is a rare infection in humans. We postulate that Janus Associated Kinase (JAK) inhibition in myeloproliferative disorders heightened this patient’s risk of bacterial translocation and severe illness in the setting of Campylobacter gastroenteritis. P. citronellolis may be identified more frequently as a pathogen in humans as more advanced diagnostic technologies become increasingly available in clinical microbiology.


INTRODUCTION
Pseudomonas citronellolis is a Gram-negative bacillus that is an unusual pathogen in humans [1,2]. Unlike other Pseudomonas species, known for their invasive nature and opportunistic characteristics, P. citronellolis infections in humans have not been extensively described in the scientific literature. Herein, we present a case of P. citronellolis bacteremia in a patient with immunosuppression, who developed septic shock after an episode of Campylobacter species gastroenteritis.

CASE PRESENTATION
An 80-year-old man with myeloproliferative disorder, characterized by a JAK2 V617F mutation on ruxolitinib, presented to the Emergency Department with several days of worsening abdominal pain. His other medical conditions included coronary OPEN ACCESS artery disease, permanent atrial fibrillation on warfarin, heart failure with a reduced ejection fraction of 38%, diet-controlled type II diabetes mellitus, and a history of prostate cancer in remission.
He reported consuming food at a restaurant a few days prior. He recalled feeling unusually fatigued and weak shortly after the event with anorexia and worsening abdominal pain over the next several days. On the day of admission, he awoke to excruciating, non-radiating, lower abdominal pain with persistent nausea, vomiting, and non-bloody diarrhea.
Initial vital signs included a temperature of 37 °C, heart rate of 100 beats per minute, blood pressure of 153/92 mmHg, respiratory rate of 22 breaths per minute, and oxygen saturation of 95 % on 5 L/min nasal cannula. Physical examination was notable for labored breathing, an irregular heart rate, marked hepatosplenomegaly, and abdominal distension. Laboratory workup revealed a white blood cell count of 6.7×10 9 cells/L, potassium of 5.8 mmol/L, creatinine of 1.71 mg/dL, total bilirubin of 1.5 mg/dL, alkaline phosphatase of 53 U/L, ALT of 22 U/L, AST of 18 U/L, and lactic acid of 2.0 mmol/L. Venous blood gas analysis was notable for a pH of 7.20, pCO 2 of 60 mmHg, and bicarbonate of 18.8 mmol/L. Computed tomography (CT) of the chest, abdomen, and pelvis revealed bilateral lower lobe atelectasis, stable severe hepatosplenomegaly, mild ascites, and no evidence of abscess or perforation. Piperacillin-tazobactam and azithromycin were started for empiric treatment of sepsis and presumptive community-acquired pneumonia. In addition, ruxolitinib was discontinued during his acute illness.
Two sets of blood cultures (BacTAlert; bioMérieux) consisting of aerobic and anaerobic bottles were collected on admission. After approximately 20 h of incubation, the automated instrument detected growth in the aerobic bottle of one set. Gram stain of the broth showed long, thin Gram-negative bacilli. Molecular testing using the GenMark ePlex (Roche Diagnostics) BCID-GN multiplex PCR panel failed to identify the organism. The blood culture bottle was sub-cultured to aerobic and anaerobic agar and incubated for 18 h. An aerobic Gram-negative bacillus was isolated. The organism was identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF; Bruker) as P. citronellolis with a confidence score of 2.277 using the Research Use Only version 4.0.11.0 BDAL library version 9. Given the unusual recovery of P. citronellolis in humans, the patient's blood sample was sent to a reference laboratory at the University of Washington for broad-range bacterial 16S rRNA gene PCR and sequencing analysis, which confirmed the presence of P. citronellolis. Susceptibility testing was performed using the Sensititre (ThermoFisher). The organism was susceptible to third-and fourth-generation cephalosporins, fluoroquinolones, aminoglycosides, carbapenems, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole.
The next day, growth was detected in the anaerobic bottle from the second set of blood cultures. Gram stain of the broth showed very long, Gram-variable bacilli, noted to look different from the Gram-negative bacilli seen in the aerobic bottle of the previous set of blood cultures. The bottle was sub-cultured to agar plates. After 1 day, no growth was observed on any of the aerobic sub-culture plates, but growth was present on the anaerobic agar. The organism was subsequently identified using MALDI-ToF as Bacteroides thetaiotaomicron, an obligate anaerobe primarily found in the gastrointestinal tract. Susceptibility testing was not performed.
Stool PCR using the Verigene Enteric Pathogen panel (Luminex) performed on admission was positive for Campylobacter species. Antibiotic susceptibilities for the Campylobacter species in his stool were not determined.
He developed hypotension requiring vasopressors, acute oliguric renal failure requiring continuous renal replacement therapy, acute respiratory failure requiring non-invasive mechanical ventilation, and delirium. Antibiotic therapy was broadened to meropenem for suspected Campylobacter-associated septicemia. Despite this, his explosive diarrhea and tense abdominal distension persisted through hospital day 5, and he experienced continued loose stools that were slow to resolve throughout his hospitalization. Stool testing for Clostridium difficile was negative. Repeat CT imaging showed no evidence of intestinal perforation, abscess, or megacolon.
He was transferred from the intensive care unit to a regular medical floor on hospital day 6 with global improvement in multiorgan failure. He received a total of 14 days of meropenem with complete resolution of symptoms. He was hospitalized for a total of 26 days and discharged to a skilled nursing facility for ongoing rehabilitation.

DISCUSSION
P. citronellolis was first described in 1960 and is considered an environmental bacterium that is typically found in the soil [1]. Although the Pseudomonas genus of Gram-negative bacilli has been extensively studied in the human host, we found only one case report of P. citronellolis infection in a human, which presented as sepsis due to a urinary tract infection and bacteremia after a transrectal ultrasound-guided biopsy in an immunocompetent individual [2]. A Medline search in June 2022, using the keyword 'Pseudomonas citronellolis' , identified 79 other articles, none of which described P. citronellolis infection in humans. We postulate that our patient's immunosuppression due to his myeloproliferative disorder and treatment with ruxolitinib heightened his risk of severe illness due to Campylobacter species infection, including his increased risk of polymicrobial bacterial translocation in the setting of gastroenteritis. Ruxolitinib is a JAK inhibitor, which mediates the signaling of various cytokines and growth factors that contribute to hematopoiesis and immune function [6]. Ruxolitinib has been associated with an increased risk of respiratory and urinary tract infections, as well as reactivation of tuberculosis, hepatitis B, Pneumocystis jirovecii, and herpes zoster infections [7]. Although severe Campylobacter infection can occasionally result in multi-organ system failure [8][9][10][11] and prior case studies have demonstrated Campylobacter bacteremia in immunocompromised hosts [12], we were unable to identify any previous cases of severe Campylobacter species infection in patients on JAK inhibitors.
In our patient, evidence of polymicrobial bacteremia without signs of gross perforation on CT imaging strongly suggests bacterial translocation or microperforation from his gastrointestinal tract. Translocation of bacteria to local structures can occur when Campylobacter damages the epithelial barrier of the gastrointestinal tract [13,14]. Cases of Campylobacter-induced enterocolitis, colitis, and toxic megacolon that have resulted in peritonitis, intestinal obstruction, and colonic perforation requiring total colectomy and ileostomy have previously been described in the scientific literature [15,16].
P. citronellolis infection in humans remains a rare entity. However, some scientists have postulated that more human isolates of P. citronellolis will be identified in the future, as more advanced diagnostic technologies, such as mass spectrometry, are increasingly used in clinical microbiology [2]. These more sophisticated clinical microbiology techniques may facilitate early identification of such organisms in the future, which is crucial in the early treatment and prevention of disease progression and fatality. Additionally, this case suggests that JAK inhibitors may increase the risk of severe illness due to Campylobacter species gastroenteritis. This case highlights the importance of preventing foodborne illness and identifying Campylobacter infection in a timely manner to avoid complications, especially in immunocompromised hosts.

Funding information
We have no funding sources to acknowledge.

Conflicts of interest
We have no conflicts of interest to declare.

Ethical statement
Our institution does not require IRB approval for case studies.

Consent to publish
Our case report includes no potential identifiers.

An Unusual Presentation of Pseudomonas citronellolisBacteremia and CampylobacterGastroenteritis Infection in a Human -A Case Report and Literature Review
Editorial Office Requirements: 1. Please include all middle name initials of authors in the manuscript and online submission system.

Thank you for pointing this out. We have included middle name initials of all authors who have middle names in the manuscript and online submission system. Drs. Elham Rahmati and Punam Verma do not have middle names.
Editor's Comments: 1. Thank you for submitting your paper to Access Microbiology, apologies for the prolonged reveiw process. You manuscript has now been reviewed and I am please to say it was well recieved by reviewers, who have recommended several minor ammendments. I would like you to revise the paper in line with the reviewers' reports and any Editorial Office requirements below. The reviewer reports can be found at the bottom of the email.
Please submit the revised version of your manuscript by 09/12/2022. If you need longer than the suggested time-frame, please contact the Editorial Office in advance to agree a different deadline at acmi@ microbiologysociety. org.
We appreciate these supportive comments. We are grateful for the opportunity to improve the clarity and rigor our manuscript based on the reviewers' comments.
We received your decision letter on Wednesday, December 7, 2022. Two of our microbiologist co-authors were out of the office until Friday, December 9, 2022, prompting us to send an e-mail to your Editorial Office at acmi@ microbiologysociety. org to request an extension for submitting our revised manuscript. We have endeavored to resubmit a high-quality revision that thoroughly addresses all reviewer comments and thank you for your consideration of our manuscript for publication as a Case Report in Access Microbiology.

Reviewer 1 Comments:
Main comments 1. In this study, the authors present a case of bacteremia and septic shock due to Pseudomonas citronellolis following Campylobacter species gastroenteritis in a patient with immunosuppression.
We are pleased that our reviewer was able to accurately and succinctly summarize the key takeaway of our manuscript.
2. Results are well presented. There is just a few minor things that are explained well and need to be revised, e.g identification of blood cultures need to be clarified.
We have revised our manuscript based on your suggestions, including clarifying the identification of blood cultures (lines 50-76).
3. Otherwise, the style and organization of the paper communicates and represents key findings in the manuscript Thank you for this positive feedback.
Smaller specific comments 4. Line 4 -..…following Camylobacter species….it should be Campylobacter with a "p" Thank you for your attention to detail. We have corrected the spelling of Campylobacter throughout the manuscript (line 4, line 25, line 106).

Line 8 -
The authors talk about Blood cultures that grew gram positive rods, this is incorrect, because gram positive rods can only be observed under a light microscope after gram staining rather than being grown on Blood agar. So, the authors need to rewrite the statement and clarify how they observed the gram positive rods.
Thank you for this helpful suggestion. We have extensively revised our discussion of blood cultures to improve the clarity, rigor, and detail of our explanation (lines 50-76).
6. Line 25 -Spelling and consistency in writing the Campylobacter throughout the manuscript Thank you for pointing this out. We have corrected the spelling of Campylobacter so that it is consistent throughout the manuscript (line 4, line 25, line 106).
7. Line 47-were the piperacillin-tazobactam and azithromycin 1stline treatment? -this needs to be clear.
We clarified that "piperacillin-tazobactam and azithromycin were started for empiric treatment of sepsis and presumptive communityacquired pneumonia" (lines 47-48).
8. Line 49-…..blood cultures grew gram-negative rods, this is a repeating statement that needs to be corrected as indicated above We appreciate this comment. As discussed in our response to Reviewer 1, comment 5, we have extensively revised our discussion of blood cultures to improve the clarity, rigor, and detail of our explanation (lines 50-76).

Line 53-Antibiotics "treatment" were broadened
We revised this sentence so that it now reads, "Antibiotic therapy was broadened to meropenem for suspected Campylobacterassociated septicemia. " (lines 79-80) 10. Lines 81 -83 have obvious mistakes, including the reference, typo, and bold text/s We have revised this sentence and ensured that it does not include typos or bolded text. The sentence now reads, "A Medline search of "(Pseudomonas putida) AND (bacteremia)", as well as "(Pseudomonas fluorescens) AND (bacteremia)" revealed 26 and 34 articles, respectively. " (lines 101-103) 11. Line 86 -Campylobacter consistency that need to be corrected We have corrected the spelling of Campylobacter throughout the manuscript (line 4, line 25, line 106).

Reviewer 2 Comments:
1. Please adjust keywords based on MeSH.
We have adjusted our keywords, such that all of our keywords are included in the Medical Subject Headings (MeSH) browser (cover page).

Please add ethical code in text body.
We appreciate this comment and agree that it is important to acknowledge the ethical code in a published manuscript. However, we feel that the body of the text is not the most appropriate place for this statement and have therefore included a statement of the ethical code on the cover page of our manuscript: "Ethics Approval: Our institution does not require IRB approval for case studies. " 3. Please discuss more on alarming results of this study in discussion section.
Thank you for this suggestion. We have strengthened our discussion to accentuate the importance of our findings and their implications for medicine and public health. In particular, we conclude our case report by stating that "this case highlights the importance of preventing foodborne illness and identifying Campylobacter infection in a timely manner to avoid complications, especially in immunocompromised hosts" (lines 130-132). 4. Minor spacing problems exist between the words in some parts of the text.
We have confirmed that all words are separated by one space throughout the manuscript. 5. Recheck all numbers in the text, to ensure their accuracy.